The armchair psychologist in me considers there to be two camps of programmer in this regard. One that gets distressed by something like not having the entire language in their head, and the other that doesn't ponder that kind of quandary in the first place.
I've shifted toward the latter as I've embraced type systems that can substitute for having the entire language in my head.
At the end of the day, I rarely care about the language. I usually just care about my data morphisms. And a good type system helps me immensely in that regard.
That's really not it. The more complex a language is, the more ways there are to approach a problem. The more things to have to learn and adapt to when reading code another engineer wrote.
You want code to be obvious. The senior engineer smiles when the junior engineer reads his code and says in just seconds "I know exactly what this does and have high confidence that it has no bugs."
